Device for preventing variation in the speed of the electrons in the case of braun tubes



5 M. VON ARDENNE v 393,468 DIQVIUE FUR PREVENTING VARIATION IN THE SPEEDUP THE ELECTRONS IN THE CASE OF BRAUN TUBES Filed NOV- 25, 1931 der)surrounding the same.

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Monte -5 2 DEVICE FOR. PREVENTING VARIATION IN THE SPEED OF THEELECTRONS IN THE CASE OF BRAUN TUBES Manfred von Ardenne, Berlin,Germany, assignor to Radioaktiengesellscliaft D. S. Loewe, Berlin-Steglitz, Germany, a company of Germany Application November 23, 1931,Serial No. 516,849 In Germany November 22, 1936 "5 Claims.

(Granted under the provisions of sec. 14, act or March 2, 1927;357 0. G.5)

Various methods are known for controlling the intensity of light in thecase of Braun tubes, such are preferably employed for televisionpurposes. Among these methods the one would appear to be very hopeful,in which the intensity of the rays is varied by an alternating potentialbetween the cathode and a cylinder (Wehnelt cylin- In place of theWehnelt cylinder it is naturally also possible to employ other elementsof control, such for example as grids. When performing control throughthe medium of elements of this nature it has been shown that the lightintensity of the fluorescent point may be reduced down to very smallamounts, without in the case of electro-statically deflected raysappreciable displacement of the point taking place by reason ofconsiderable variations in speed. By the use of control electrodes ofthis nature, in which the control field is substantially transverse tothe field of acceleration of the anode, and more particularly,therefore, when employing cylindrical electrodes, such for example asthe Wehnelt cylinder, it may be accomplished that the concentration ofthe rays may also be well maintained. By reason of the cylinder or gridpotential the form of the charge cloud surrounding the cathode, andaccordingly the eflective cathode surface, is varied.

A certain it only a very small efiect on the speed of the electronspreventing proper utilization of the fundamentally existingpossibilities of the Braun tube nevertheless remains. The extent of thevariation in speed in the case of control between light and dark isapproximately between 5 and 10%. As to be expected theoretically, thedirection is also such that in the case of a strong negative biaspotential, i. e., when approaching the extreme state dark the speed ofthe electrons diminishes. This according to the inventin may beprevented in simple manner by causing'the anode potential to fluctuatewith corresponding amplitude in counter-phase to the fluctuations inintensity.

The variation in speed may in practice be compensated in very simplefashion for a lengthy and, generally speaking, undoubtedly sufllcientinterval in the intensity. If a purely ohmic resistance is included inthe anode circuit, it is accomplished that at the moments ofconsiderable ray currents, i. e., of great intensity, due to theincreased potential spacing, which increases simultaneously withincreasing anode current, a smaller anode, potential exists than at themoments of weaker currents.

The mug iavourable value for the resistance may be discovered in verysimple fashion by the fact that when passing the potential to theintensity control the resistance is brought to that value at which, indeflected state, the point or edge of the image appears with optimalsharpness. Experiments have shown that the most favourable value for theresistance when employing the tubes produced by the applicant wassituated in the order of 10 ohms. i

A form of embodiment of the invention is illusm trated in the drawing.In the latter, 1 is a Braun tube having the cathode 2, the anode 3, theWehnelt cylinder 4 and the deflecting plates 5. The cathode is heated bya battery 6, while the necessary negative bias potential is conducted to5 the Wehnelt cylinder from the grid battery '7 over the secondary coil8 of the control transformer 9. The potential for controlling theintensity. of light is applied to'the terminals 10 of the primary coil11 of the control transformer 9. 20 The anode potential is supplied bythe battery 12, which is connected with the anode 3 over the resistance13 according to the invention.

I claim:

1. In a television arrangement a Braun tube gs having a cathode forgenerating a cathode ray, an anode, a picture screen, means fordeflecting said cathode ray and means for controlling the intensity ofsaid cathode ray, means for generating an anode, a picture screen, meansfor deflecting 40 said cathode ray, and means for. controlling theintensity oi. said cathode ray, means for generating deflecting voltagescontrolling said deflecting means, means ior generating a controlvoltage controlling said intensity controlling means, 45 and means forcompensating the disturbing varia; tions in velocity of said cathode rayresulting from the intensity control thereof, said compensating meansvarying the anode potential in counterphase to said disturbingvariations, and'compris- .50

ing a resistance in the anode circuit.

3. In a television arrangement a Braun tube having a cathode forgenerating a cathode ray, an. anode, a picture screen, means fordeflecting said cathode ray, and means for controlling the in- 56tensity of said cathode ray, means for generating deflecting voltagescontrolling said deflecting means, means for generating a controlvoltage controlling said intensity controlling means, and means forcompensating the disturbing variations in velocity of said cathode rayresulting from the intensity control thereof, said compensating meansvarying the anode potential in counterphase to said disturbingvariations, and compristhe anode potential in counter-phase to saiddisturbing variations, and comprising a resistance in the order of 10ohms in the anode circuit.

5. In a television arrangement a Braun tube having a cathode forgenerating a cathode ray, an anode, a picture screen, means fordeflecting said cathode ray, and means for controlling the intensity ofsaid cathode ray, means for generating deflecting voltages controllingsaid deflecting means, means for generating a control voltagecontrolling said intensity controlling means, and means for compensatingthe'disturbing variations in velocity of said cathode ray resulting fromthe intensity control thereof, said compensating means varying the anodepotential in counterphase to said disturbing variations, and comprisinga resistance in the anode circuit, the optimal value of said resistancebeing acflusted by obtaining optimal sharpness of the fluorescent pointupon deflection.

' MANFRED vou ARDENNE.

